This invention relates to a capacitance sensing apparatus for use in a position sensing system.
Capacitive proximity sensing is well known in the prior art. By measuring changes in capacitance across two conductors, a suitable circuit can detect the proximity of a capacitive object, including body parts such as a human finger. The change in capacitance generally increases as the object approaches the conductors. This effect can be used in a data input device, such as the simulation of a simple button, by determining when the capacitance across the conductors has changed by a given amount compared to a rest state.
U.S. Pat. No. 5,565,658 discloses a touch sensitive panel whereby a matrix of conductors are provided in an array. The conductors are in two layers; a first layer comprising a plurality of elongate “horizontal” conductors; and a second layer comprising a plurality of elongate “vertical” conductors in the same plane as the horizontal conductors and having their length perpendicular to the length of the horizontal conductors. By measuring the changes in capacitance of each pair of horizontal and vertical conductors, the location of an object pressing on or approaching the panel can be determined.